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Chevy39 08-31-2006 03:37 PM

Tune port injection vs. throttle body injection
I am building a 39 chevy sedan. I am planning on using a new 350 like came in the 94 chevrolet pickups. The 94 pickup i have gets about 18 mpg with throttle body injection. Tune port injection looks good on a street rod, but is there any advantage to it. I can get a throttle body injection system complete at a pretty cheap price, but The TPI seems to be about $300 to $400 and most of them require me to get the 90-92 computer for speed density sensor. I know that most of TPI injections i have ran across are from 305's and will need the injectors upgraded to the 350 ones. That will run over a couple hundred dollars. So is it really worth the extra money to go tune port over throttle body? I am building a driver car, not a drag car and on a limited budget. Saving money to build a new house. I am running a 700R4 from a 89 Camaro and a 3.40 gear in an 8" rear-end. Thanks for any info, Steven

olescarb 08-31-2006 03:43 PM

you can't for the time being beat a modern carb set up for power but if you have the time and money port injection is a nice set up, TBI is good but the injectors have limited flow so if you build a hot engine it may be more problems than it is worth. Now for off road injection (TBI or port) is the only real option.

henry @ oles

1931 steve 08-31-2006 03:47 PM

All depends on what you want to do with the engine.

The TBI is good for factory engines and has a good cold start and idle at any temp. The TPI looks better performs better and I thing has a better idle quality.

If you compare induction to induction I think the TPI wins hands down. Better performance, better fuel economy, and better looking.

I have a complete TPI set up with the upgraded runners, just waiting to be installed on a engine, problem is I have had this set up for at least 2 years, but since upgraded to a LT1 engine. So the TPI just sits on the shelf. I think for the money the TPI is worth it. Just my .02


Rick WI 08-31-2006 04:27 PM

Henry is right, it's hard to beat a very well setup carb and intake system for the street. My choice for performance is ALWAYS a well setup Holley HP.

BUT, a poor carb setup to EFI is like apples and footballs. The last retro we did was a 400 SBC from an Edelbrock carb and intake to a TPI controlled by a F.A.S.T. EFI system. The customer was EXTREMELY pleased with how it ran.

The trouble though with the stock TPI is it's not going to make horsepower. This application was in a truck with aftermarket runners. Still not a HP king at all but it made 450 ft/lbs of torque under 3000 RPM on the dyno. That's SAE corrected as well. Not foo foo magazine numbers.

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